pcmhacking.net

so my Gemini is running a VR V6 alternator (85amp) and I believe I am getting to the limits of its capacity, so I wanted to throw the question out there .... does anyone know of a bolt in replacement that is 100-120amps or so ?

or is the stock one able to be upgraded to handle more .... I don't really know enough about this side of them to know what the options are....

what size cable you got going from alt to battery most people dont even have enough cable to even flow the full 85amps if it tried. you can get the BT1 alt its 100amp for police cars with lights and radios etc.avoid the cheap 100amp 1 wire alternators they tend to have winding wire diamters so thin they dont support 100amps for long LOL

Must be that big sub woofer you running, the one that makes it vibrate down the track so quick lol

thats a good thought .... i can't remember the amps of that cable, but its not 85amps i don't think, its like probably 3-4mm at the most, fine core but other than that nothing special ....

i also have the battery in the boot so the alternator has to go to there to be on the battery side of the kill switch .....

i've worked out so far, 2 x 044 pumps is about 16 amps each, plus a 10amp lift pump, the two fans are about 15 i think, plus the 6 x LS2 coils, im not sure on their usage, but even if they are 5 amps each (probably more) all that is nearly 100amps ... plus computer, igntion module, and headlights!

i have the main power from the starter motor to the fuse panel so i might try and run an alternator wire to there aswell just to see .....

basically, idling, its 13.7v then when the fans come on it drops to 13.2v, then with the headlights on it drops to 12's and i've seen racing logs with 11's .... (second pump on with boost)

there are 120amp alternators to suit a VN-VR so might be an option if all else fails, but might be just the alternator -> battery main wire i need so will check that first!

HQ355 wrote:Must be that big sub woofer you running, the one that makes it vibrate down the track so quick lol

this is the first car i have ever owned that i am pushing the alternator, and its not even a stereo thats the issue lol! technology needs lots of amps!

Holden202T wrote: i also have the battery in the boot so the alternator has to go to there to be on the battery side of the kill switch .....

i have the main power from the starter motor to the fuse panel so i might try and run an alternator wire to there aswell

I have always run the alternator output to the starter cable with a boot mounted battery. You could also put a large diode across the isolator (anode to the engine side, cathode to the battery side) to clamp the alternator output voltage in the event of the isolator being opened at significant RPM. If the alternator is able to support all of the load then opening the isolator may not kill the engine.

Simon

yeah thats the problem and thats why the alternator cable runs to the boot because otherwise the engine wouldn't stop, and it has to kill all power to the engine etc in the event of an emergency from outside the car.

If you have an auxiliary contact on the isolator it could open the alternator field circuit, killing the charge. Could also use this to kill the ECU. Will have a think on other ways to detect the isolator opening.

Simon

I am surprised that the 85 amp is not enough. What exactly are you using that is drawing so much current? If your got the battery in the boot do you also have the sensing wire running there as well? You can easily boost the voltage output by fitting a diode between the regulator and (I think, it's been a long time) the field winding. This will get it to put out an extra 0.6 volts but no tricks to boost current.

Holden202T wrote: i also have the battery in the boot so the alternator has to go to there to be on the battery side of the kill switch .....

Why? Is your kill switch in the boot too?

im more inclined to think delcowizzids suggestion might be the path to look down ....

so battery in the boot to make room for turbo and 202 in the engine bay etc ... then it has a 13 or 15mm i can't remember, but it was the largest cable i could get, which runs from the battery to the isolator switch which is on the rear of the boot (where the number plate normally is) then it goes to the starter motor from there. and on the battery side of the isolator switch is the charging wire from the alternator .... i've just checked and it is only about 10-12 gauge running from alternator to battery ....